Search Results (279)

TiVCr-based alloys are well-explored body-centered cubic (BCC) materials for hydrogen storage applications that can potentially store higher amounts of hydrogen at moderate temperatures. The challenge remains in optimizing the alloy-hydrogen stability, and several transition elements have been found to support the reduction in the hydride stability. In this study, Ni and Nb transition elements were incorporated into the TiVCr alloy system to thoroughly understand their influence on the (de)hydrogenation kinetics and thermodynamic properties. Three different compositions, (TiVCr)₉₅Ni₅, (TiVCr)₉₀ Ni₁₀, and (TiVCr)₉₅Ni₅Nb₅, were prepared via arc melting. The as-prepared samples showed the formation of a dual-phase BCC solid solution and secondary phase precipitates. The samples were characterized using hydrogen sorption studies. Among the studied compositions, (TiVCr)₉₀Ni₁₀ exhibited the highest hydrogen absorption capacity of 3 wt%, whereas both (TiVCr)₉₅Ni₅ and (TiVCr)₉₀Ni₅Nb₅ absorbed up to 2.5 wt% hydrogen. The kinetics of (de)hydrogenation were modeled using the JMAK and 3D Jander diffusion models. The kinetics results showed that the presence of Ni improved hydrogen adsorption at the interface level, whereas Nb substitution enhanced diffusion and hydrogen release at room temperature. Thus, the addition of Ni and Nb to Ti-V-Cr-based high-entropy alloys significantly improved the hydrogen absorption and desorption properties at room temperature for gas-phase hydrogen storage. Full article

Water within coal reservoirs exerts dual effects on methane adsorption–desorption by competing for adsorption sites and reducing permeability. The bound water effect, caused by coal wettability, significantly constrains coalbed methane (CBM) production, rendering investigations into coal wettability crucial for efficient CBM development. Compared with other geological formations, coals are characterized by a highly developed microporous structure, making the CO₂ sequestration mechanism in coal seams closely linked to the microscale interactions among gas, water, and coal matrixes. However, the intrinsic mechanisms remain poorly understood. In this study, molecular dynamics simulations are employed to investigate the wettability behaviors of CO₂, CH₄, and water on different coal matrix surfaces under varying temperature and pressure conditions, for coal macromolecules representative of four coal ranks. The study reveals the evolution of water wettability in response to CO₂ and CH₄ injection, identifies wettability differences among coal ranks, and analyzes the microscopic mechanisms governing wettability. The results show the following: (1) The contact angle increases with gas pressure, and the variation in wettability is more pronounced in CO₂ environments than in CH₄. As pressure increases, the number of hydrogen bonds decreases, while the peak gas density of CH₄ and CO₂ increases, leading to larger contact angles. (2) Simulations under different temperatures for the four coal ranks indicate that temperature has minimal influence on low-rank Hegu coal, whereas for higher-rank coals, gas adsorption on the coal surface increases, resulting in reduced wettability. Interfacial tension analysis further suggests that higher temperatures reduce water surface tension, cause dispersion of water molecules, and consequently improve wettability. Understanding the wettability variations among different coal ranks under variable pressure–temperature conditions provides a fundamental model and theoretical basis for investigating deep coal seam gas–water interactions and CO₂ geological sequestration mechanisms. These findings have significant implications for the advancement of CO₂-ECBM technology. Full article

Magnesium whitlockite (Mg-WH) has emerged as a promising biomaterial for bone regeneration due to its compositional similarity to natural bone minerals. This study aimed to systematically modify a dissolution–precipitation synthesis method to produce Mg-WH granules with tailored morphologies and controlled phase compositions for possible use in bone regeneration applications. Three distinct precursor granules were prepared by mixing varying amounts of ammonium dihydrogen phosphate and magnesium hydrogen phosphate with calcium sulfate. The precursors were then transformed into biphasic and single-phase Mg-WH granules by means of immersion in magnesium- and phosphate-containing solutions under controlled conditions. The X-ray diffraction results demonstrated that biphasic materials containing Mg-WH and either calcium-deficient hydroxyapatite (CDHA) or dicalcium phosphate anhydrous (DCPA) formed after 24 h of synthesis, depending on the synthesis conditions. Prolonging the reaction time to 48 h resulted in complete transformation into single-phase Mg-WH granules. Fourier-transform infrared spectroscopy confirmed the presence of functional groups characteristic of Mg-WH, CDHA, and DCPA in the intermediate products. The spectra also indicated the absence of precursor phases and the progressive elimination of secondary phases as the reaction time increased. Scanning electron microscopy analyses revealed notable morphological transformations from the raw granules to the product granules, with the latter exhibiting interlocked spherical and rod-like particles composed of fine Mg-WH rhombohedral crystals. N₂ adsorption–desorption analyses exposed significant differences in the surface properties of the synthesized granules. By varying precursor, reaction solution compositions, and reaction times, the study elucidated the phase evolution mechanisms and demonstrated their impact on the structural, morphological, and surface properties of Mg-WH granules. Full article

As a kind of clean energy, hydrogen energy has great potential to reduce environmental pollution and provide efficient energy conversion, and the key to its efficient utilization is to develop safe, economical and portable hydrogen storage technology. At present, hydrogen storage technology lags behind hydrogen production and use, which is the bottleneck restricting the development of hydrogen energy. In this paper, several current solid-state hydrogen storage methods are reviewed, including hydrate hydrogen storage, alloy hydrogen storage and MOF hydrogen storage. At the hydrogen storage density level, the hydrogen storage capacity of 1K-MOF-5 can reach 4.23 wt% at 77 K and 10 MPa, and remains basically unchanged in 20 isothermal adsorption and desorption experiments. At the level of temperature and pressure of hydrogen storage, the alloy can realize hydrogen storage under ambient conditions. At the economic level, the cost of hydrogen storage in hydrates is only USD 5–8 per kilogram, with almost zero carbon emissions. Through the analysis, it can be seen that the above solid-state hydrogen storage technologies have their own advantages. Although hydrate hydrogen storage is lower than alloy materials and MOF materials in hydrogen storage density, it still has huge potential for utilization space because of its low cost and simple preparation methods. This paper further provides a comprehensive review of the existing challenges in hydrate research and outlines prospective directions for the advancement of hydrogen storage technologies. Full article

Hexagonal ZnO nanowires were grown using the PLD/VLS technique on a SAW sensor active area for hydrogen sensing. The influence of different carbon and nitrogen surface contaminant concentrations on sensor output was investigated for three active area cases: a few weeks’ exposure to free ambient air contamination, 3 h at 600 °C thermal desorption of carbon, and (room temperature) plasma-activated nitrogen and carbon contamination. Correlations between sensing performance and contamination element concentration were established. To understand the adsorption versus absorption mechanisms, similar studies were further performed on circular ZnO nanowires morphology, which have a different surface-area-to-volume ratio. Comparative results show that, while a 20% carbon surface contamination variation generates a variation of 3–5% in nanostructure hydrogen sorption, nitrogen surface contamination influence depends on nanostructure morphology. Thus, in our comparative studies, for the case of a nanowire hexagonal cross-section a 12% nitrogen surface contamination variation generates a 5–7% increase in hydrogen adsorption and also an increase of 6–8% in hydrogen absorption. Consequently, the catalytic effect of nitrogen could enlarge the linear response of nanowire-based (SAW) sensors over a wider hydrogen concentration range. Full article

Addressing the removal of hazardous phenolic pollutants from water, this study introduces an eco-friendly adsorbent composed of waste-derived hydrochar immobilized in alginate beads (Alg/HC). The physicochemical properties of the Alg/HC beads were characterized using SEM, XRD, and FTIR, confirming hydrochar encapsulation and partial structural preservation. Batch studies revealed a maximum 2-nitrophenol (2-NP) adsorption capacity of 15.80 ± 0.62 mg/g at 30 mg/L of 2-NP, with kinetics best described by the Elovich and pseudo-second-order models. Freundlich isotherm fitting indicated multilayer adsorption on heterogeneous surfaces, likely governed by hydrogen bonding and π–π interactions. In a fixed-bed column system, Alg/HC beads demonstrated a continuous adsorption capacity of 6.84 ± 0.45 mg/g at 10 mg/L of 2-NP, with breakthrough behavior modeled by the Yoon–Nelson and Thomas equations. The beads maintained stable performance across four regeneration cycles using a mild water/ethanol desorption method. This work represents the first study to explore Alg/HC composites for 2-NP removal in both batch and continuous modes, demonstrating their potential as low-cost, regenerable adsorbents for tertiary treatment of phenolic industrial wastewater. Full article

A novel 3-amino-5-mercapto-1,2,4-triazole functionalized graphene oxide composite (GO-ATT) was successfully prepared via a covalent coupling method, then employed for the removal of p-nitrophenol (PNP) from wastewater. The morphology as well as the composition of GO-ATT composite were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS). The surface charge of GO-ATT composite was evaluated by Zeta potential analyses. The surface area and pore size distribution of GO-ATT composite were analyzed using specific surface analyses using the Brunauer–Emmett–Teller (BET) method. Batch adsorption experiments were performed to investigate the effects of conditional factors, including contact time, solution pH, initial PNP concentration, and contact temperature, on the adsorption process. A maximum adsorption capacity of PNP by GO-ATT composite (0.287 mmol g⁻¹) could be obtained at 25 °C. Freundlich isotherm (R² > 0.92505) can better describe the adsorption behavior of PNP on GO-ATT composite. The thermodynamic functions (ΔG°, ΔH°, ΔS°) indicate that adsorption is a spontaneous, endothermic, entropy-increasing process and features physisorption. The adsorption behavior of PNP on GO-ATT composite conformed to the nonlinear pseudo-second-order kinetic model. Adsorption mechanism investigation indicated that the electrostatic, π-π stacking, and hydrogen bonding interactions were involved in the adsorption process. After 10 adsorption–desorption cycles, the adsorbent exhibited a stable and efficient removal rate (94%) for PNP. Due to its advantages of a high efficiency, excellent reusability, and high stability, the covalently coupled GO-ATT composite might be used as an effective adsorbent for the removal of phenolic contaminants from wastewater. Full article

The transformation of abundant and cost-effective CO₂ molecules into valuable chemical feedstocks or fuels represents an appealing yet challenging research objective. Artificial photosynthesis offers a promising pathway for CO₂ reduction reactions (CO₂RR) under mild and environmentally friendly conditions. Graphitic carbon nitride (g-C₃N₄) has attracted significant attention for its potential to enhance the efficiency and selectivity of CO₂RR through synthesis and modification strategies. This review explores recent advancements in g-C₃N₄ and its hybrid photocatalysts for selective CO₂ conversions. We examine key factors influencing CO₂RR product selectivity, including electron count and reaction dynamics, CO₂ and reduction intermediates adsorption/desorption, and proton regulation affecting competitive hydrogen evolution. By summarizing various strategies to enhance CO₂ photoreduction performance, this work provides a comprehensive analysis of CO₂RR selectivity mechanisms for each approach. This review aims to inspire research endeavors towards developing efficient artificial systems for enhanced CO₂RR efficiency and product selectivity. Full article

β-carotene (β-C) is a hydrophobic compound, easily degradable by light and oxygen and with low solubility, limiting its applications. β-cyclodextrin (β-CD) can encapsulate β-C, protecting it from degradation and maintaining its bioactivity. Therefore, this research aimed to characterize and determine the antioxidant and erythroprotective activity of β-C/β-CD inclusion complexes. The co-precipitation technique was used to elaborate β-C/β-CD in a 40:60 ratio, obtaining a high yield (94.10%), an entrapment efficiency of 82.47%, and a loading efficiency of 11.92%. The moisture of β-C/β-CD was 2.93%. β-C release increased over the time of 216 h (80.8%, 92.8%, and 97.4% at 8 °C, 25 °C, and 37 °C, respectively). A UV–visible analysis confirmed the presence of β-carotene in the inclusion complex, indicating successful encapsulation without significant structural changes. According to the adsorption–desorption isotherms, the complexes showed a type II isotherm. The FT-IR and Raman spectroscopy confirmed the formation of the inclusion complex, which interacted by hydrogen bonds, hydrophobic interactions, or van der Waals forces. The DSC showed an endothermic peak at 118 °C in the β-C/β:CD. The TGA revealed reduced water loss in the β-carotene/β-cyclodextrin complex, indicating limited water binding due to encapsulation. The microscopic surface morphologies observed by the SEM of β-C/β-CD were irregular-shaped clumps in the surface with a particle average size of 8.09 µm. The X-ray diffraction showed a crystalline structure of the complex. The zeta potential determination indicated a negative charge (−23 and −32 mV). The ABTS, DPPH, and FRAP demonstrated the antioxidant activity of β-C/β:CD (34.09%, 21.73%, and 8.85. mM ET/g, respectively), similar to pure β-C (34.64%, 22.63%, and 9.12 μM ET/g, respectively). The complexes showed an erythroprotective effect inhibiting hemolysis (64.09%). Therefore, with these characteristics, β-CD is a good encapsulant for β-C, and this complex could be applied in the food and pharmaceutical industries. Full article

In this study, an effective composite material, manganese-modified magnetic dual-sludge biochar (Mn@MDSBC), was developed for the adsorption of ciprofloxacin hydrochloride (CIP). This composite was prepared by means of a simple one-pot method, which involved the pyrolysis of iron-based waterworks sludge (IBWS) and paper mill sludge (PMS) loaded with manganese (Mn) under controlled conditions in a nitrogen atmosphere. The synthesized Mn@MDSBC was subjected to a comprehensive suite of characterization approaches, which included N₂ adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Subsequently, static adsorption tests were conducted to investigate how different factors, including the initial solution pH, reaction time and temperature, CIP concentration, and ionic strength influence the adsorption of CIP by Mn@MDSBC. Mn@MDSBC had the maximum CIP adsorption capacity of 75.86 mg/g at pH 5, among the pH values ranging from 3 to 9. The pseudo-second order model provided the best description of the adsorption process, while the experimental data aligned more closely with the Langmuir equation than with the Freundlich model, indicating monolayer adsorption. The adsorption process was found to be non-spontaneous and exothermic according to thermodynamic analysis. The presence of Cl⁻ and SO₄²⁻ enhanced CIP adsorption, while PO₄³⁻ weakened it. After five cycles of reuse, Mn@MDSBC experienced a 17.17% loss in CIP adsorption capacity. The primary mechanisms for CIP removal by Mn@MDSBC were identified as physical and chemical adsorption, hydrogen bonding, and π-π stacking interactions. In summary, the study underscores the high efficiency of Mn@MDSBC as a composite material for CIP adsorption, highlighting its potential for application in wastewater treatment processes. Full article

Biochar has attracted considerable interest owing to its high adsorption capacity; however, the mechanisms through which environmental factors influence the release of adsorbed pollutants remain unclear. This study investigates the adsorption and desorption dynamics of Rhodamine B (RhB) on biochars B2 and B6, which were pyrolyzed at temperatures of 200 °C and 600 °C, respectively, under varying conditions. The results indicated that there was no significant difference in removal efficiency at low RhB concentrations; however, at a concentration of 600 mg/L, biochar B2 had a higher removal efficiency than B6, likely attributable to more adsorption sites. Increased temperatures were found to enhance desorption from both B2 and B6, with B6 exhibiting a faster desorption rate. This phenomenon may be due to the stronger hydrogen bonding between B2 and RhB, which could inhibit desorption. In addition, elevated pH values facilitated desorption, presumably through electrostatic repulsion. Under alkaline conditions, B2 released a greater amount of dissolved organic matter (DOM), leading to increased RhB desorption relative to B6. This study offers a valuable reference for evaluating the environmental risk associated with the application of biochar in real-world settings. Full article

Background/Objectives: The persistence of tetracycline residues in aquatic environments poses substantial risks to ecosystems and public health, emphasizing the need for effective removal strategies. This study examines the use of purified stevensite (ST), a natural clay mineral, as an efficient and cost-effective adsorbent for removing tetracycline antibiotics from contaminated water. Methods: Batch experiments were conducted to assess the adsorption kinetics, isotherms, and influence of environmental factors. Material characterization studies were performed before and after tetracycline adsorption. Results: ST demonstrated optimal removal efficiency at an acidic pH, achieving over 99% elimination of both tetracyclines and their metabolites at an adsorbent dose of 2 g L⁻¹ and antibiotic concentration of 5 mg L⁻¹. Equilibrium was reached within 30 min. Regeneration experiments confirmed that ST retained over 90% of its adsorption capacity after five adsorption–desorption cycles. Surface characterization revealed that ST’s large surface area, high cation exchange capacity, and potential for hydrogen bonding may explain its high adsorption capabilities. The material was tested on real samples of tap water, surface water, and wastewater, demonstrating an effective removal rate over 99%. Conclusions: With its high efficiency, low cost and favourable reusability, purified ST is a promising option for large-scale wastewater treatment, contributing to safer water resources and improved environmental protection. Full article

Graphene, being a two-dimensional monolayer of carbon, exhibits an exceptionally increased surface-to-volume ratio due to its atomic thinness and high aspect ratio, making it a material of considerable interest in advanced technology applications. Recent developments have leveraged their unique surface characteristics, such as nanoscale ripples and grooves, to enhance energy storage, sensing, catalysis, and environmental remediation performance. Its extensive surface area enables rapid ion adsorption and desorption, significantly improving energy and power densities in supercapacitors and lithium-ion batteries while enhancing stability over prolonged cycles. In sensing, the high surface-to-volume ratio supports the immobilization of biomolecules and nanoparticles, improving sensitivity in detecting gases, biomarkers, and pollutants, thereby advancing diagnostic and environmental monitoring applications. Its expansive surface area and unique electronic properties contribute to high catalytic efficiencies, enabling sustainable chemical processes, such as hydrogen production, water treatment, and pollutant degradation. Unlike many review articles that primarily explore the functionalization of graphene, this study mainly emphasizes the evaluation of methodologies aimed at augmenting graphene’s surface area. This review systematically evaluates recent advancements in the optimization of graphene surface characteristics, with a primary focus on their role in enhancing energy storage systems while also addressing emerging applications in healthcare and environmental sustainability. Full article

In this work, zeolitic imidazolate frameworks (ZIF-8, ZIF-67, and ZC-ZIF) and their hybrid composites with carboxylate-functionalized carbon nanotubes (fCNTs) are synthesized through low-cost synthesis methods for enhanced physisorption-based hydrogen storage at room temperature. While both base and hybrid structures are designed to improve hydrogen uptake, the base materials exhibit the most notable performance compared to their carbon hybrid counterparts. The structural analysis confirms that all samples maintain high crystallinity and exhibit well-defined rhombic dodecahedral morphologies. The hybrid composites, due to the intercalation of fCNTs, show slightly larger particle sizes than their base materials. X-ray photoelectron spectroscopy reveals strong nitrogen–metal coordination in the ZIF structures, contributing to a larger specific surface area (SSA) and optimal microporous properties. A linear fit of SSA and hydrogen uptake indicates improved hydrogen transport at low pressures due to fCNT addition. ZIF-8 achieves the highest SSA of 2023.6 m²/g and hydrogen uptake of 1.01 wt. % at 298 K and 100 bar, with 100% reversible adsorption. Additionally, ZIF-8 exhibits excellent cyclic repeatability, with only 10% capacity reduction after five adsorption/desorption cycles. Kinetic analysis reveals that hydrogen adsorption in the ZIF materials is governed by a combination of surface adsorption, intraparticle diffusion, and complex pore filling. These findings underscore the potential of ZIFs as superior materials for room-temperature hydrogen storage. Full article

Copper-containing catalysts supported on different commercial oxide supports (SiO₂, Al₂O₃, and mixed oxide supports) were prepared by the incipient wetness impregnation method and investigated for the selective hydrogenation of methyl esters (methyl butyrate, methyl hexanoate, methyl stearate) to fatty alcohols. Characterization techniques, including transmission (TEM) and scanning electron microscopy (SEM), X-ray diffraction (XRD), N₂ adsorption–desorption isotherms, and the temperature-programmed hydrogen reduction (H₂-TPR) method, were utilized and revealed the relationship between catalyst properties and its structure. The best results of catalytic activity were obtained in the presence of the Cu catalyst supported on SiO₂ with co-precipitated Al₂O₃, where the conversion of esters was above 50% with a selectivity for the corresponding alcohols of 40–70%. This efficient and inexpensive Cu-based catalyst can be widely used in industrial production, which is conducive to promoting the development of non-precious metal catalysts in the biomass industry. Full article